2.1. Field of the Invention
The exemplary, illustrative, technology herein relates to power manager systems suitable for operably connecting one or more power sources and one or more power loads to a power bus and distributing power from the power sources to the power loads over the power bus. The improved power manager includes at least one universal port that can be operated as an input port to receive input power from a power source and that can also be operated as an output port to deliver output power to a power load. Additionally the improved power manager includes system and operating method improvements provided to reduce power loss stemming from DC to DC power conversions.
2.2. The Related Art
Referring to FIGS. 1 and 2, a conventional power manager (100, 200) includes a Direct Current (DC) power bus (105) and six power ports (110, 130) operably connectable with the power bus. Up to six external power devices (115, 120) can be connected, one to each of the six device ports (110), and all six external power devices can be operably connected to the power bus (105) simultaneously. In one particularly relevant embodiment disclosed in U.S. Pat. No. 8,633,619 to Robinson et al. entitled Power managers and method for operating power managers, issued on Jan. 21, 2014; a power manager is disclosed that includes six device ports. The power manager system disclosed by Robinson et al. is shown schematically in FIGS. 1 and 2. In FIG. 1, a power manager (100) includes six device ports with two input device ports (130) and four output device ports (110). When all the device ports are connected to external power devices each device port (110, 130) is connected to an input power or energy source (115) or to a power load (120).
Each device port is operably connectable to a power bus (105) by operating one or more controllable switches. In an initial state each controllable switch is open (shorted) to disconnect the device port from the power bus. An electronic controller (125, 205) operates the controllable switches according to an energy management schema program or firmware running on the electronic controller. The electronic controller also communicates with each external device (115, 210) or with a smart cable associated with the external device to determine its operating voltage range and other power characteristics. The electronic controller continuously monitors external devices connected to the device ports and continuously evaluates if each connected external power device is a power source or a power load and further determines whether the external power device can be connected to the power bus (105) or not. In the event that the electronic controller determines that the connected external device is not compatible with connecting to the power bus the device is not connected. In the event that the electronic controller determines that an external device already connected to the power bus is no longer compatible with connecting to the power bus the device is disconnected by actuating a controllable switch.
The power manager (100, 200) is configured as a Direct Current (DC) device suitable for use with DC power sources and DC power loads. The conventional power bus (105) operates at a substantially fixed DC voltage. While the fixed bus DC voltage may fluctuate as power loads and power sources are connected to or disconnected from the power bus (105) the power bus voltage is substantially maintained within a small voltage range, e.g. 10-14 volts or the like, referred to herein as a “bus-compatible voltage.”
When an external power device (115, 120) is determined to be operable at a bus-compatible voltage the external power device (115, 120) is preferably directly connected to the power bus without any power conversion. Thus power sources and power loads that can operate at the bus-compatible voltage can be directly connected to the power bus (105) over any one of the device ports (110) or (130) without the need for a voltage conversion. This is demonstrated in FIG. 2 which shows a schematic representation of a pair of input device ports (130a) and (130b) each connectable to the power bus (105) over two different connection paths and a pair of output device port (110a) and (110b) each connectable to the power bus (105) over two different connection paths. As shown, each input device port (130a, 130b) includes a first power channel (1080) that extends between the device port (130a) and the power bus (105) and another first power channel (1085) that extends between the device port (130b) and the power bus (105). As also shown each first power channel (1080, 1085) includes a first controllable switch (1040) disposed between port (130a) and the power bus and first controllable switch (1030) disposed between port (130b) and the power bus. Similarly each output port (110a, 110b) also includes a first power channel (1090, 1095) and a first controllable switch (1055) disposed between the output port (110a) and the power bus (105). Thus all six device ports include a first power channel for directly connecting an external device connected to the device port to the power bus when the first controllable switch is closed.
In operation the first controllable switch is opened preventing the external device from connecting with the power bus (105). The electronic controller (125) communicates with each external power source (115a, 115b) and with each external power load (120a, 120b) to determine operating voltages of each externally connected power device. If any of the connected external devices are operable at the bus compatible voltage the electronic controller (125) can actuate (close) the relevant first controllable switching elements (1030, 1040, 1055, 1060) to directly connect all of the external devices that can operate at the bus voltage to the power bus if other conditions of the energy management schema justify the connection. Moreover in the case where a power source or a power load is operable at the bus compatible voltage power sources (115a, 115b) and the power loads (110a, 110b) are interchangeable between the input device ports (130a, 130b) and the output ports (110a, 110b). More generally every device port (110) can be used as in input device port or an output device port when the connected external device is operable at the bus-compatible voltage.
Alternately when a connected external device is not operable at the bus-compatible voltage it can be connected to the power bus over a DC to DC power converter when the power converter is configurable to perform a suitable voltage conversion. This is demonstrated in FIG. 2 wherein the two input device ports (130a, 130b) share a single input power converter (1065) and the two output device ports (110a, 110b) share a single output power converter (1070). Each power converter (1065) and (1070) is unidirectional such that the power converter (1065) can only make a power conversion on an input power signal received from a power source (115a, 115b) and the power converter (1070) can only make a power conversion on an output power signal received from the power bus (105).
The input ports (115a, 115b) share the input power converter (1065) over a second power channel (1075). The channel (1075) is accessed by the device port (130a) by opening the switches (1040) and (1035) while closing the switch (1025) such that a power signal received through the input device port (130a) flows over the second power channel (1075) and through the power converter (1065) to the power bus (105). The channel (1075) can also be access by the device port (130b) by opening the switches (1030) and (1025) and closing the switch (1035) such that a power signal received through the input device port (130b) flows over the second power channel (1075) and through the power converter (1065) to the power bus (105). Thus one of the two input power sources (115a) and (115b) can be connected to the power bus over the input power converter via the second power channel (1075), both of the two input power sources (115a) and (115b) can be connected to the power bus over the two first power channels (1080) and (1085) or one of the two input power sources (115a) and (115b) can be connected to the power bus over the input power converter via the second power channel (1075) while the other of the two input power sources (115a) and (115b) is connected to the power bus over the relative first channel (1080) or (1085).
Similarly the output ports (110a, 110b) share the output power converter (1070) over a second power channel (1097). The channel (1097) is accessed by the device port (110a) by opening the switches (1045) and (1055) while closing the switch (1050) such that a power signal flowing from the power bus (105) to the output port (110a) flows through the output power converter (1070) and over the second power channel (1095) to the power load (120a). The channel (1075) can also be accessed by the device port (110b) by opening the switches (1050) and (1060) and closing the switch (1045) such that a power signal flowing from the power bus (105) to the output port (110b) flows through the output power converter (1070) and over the second power channel (1095) to the power load (120b).
Thus one of the two power loads (120a) and (120b) can be connected to the power bus over the output power converter via the second power channel (1097), both of the two power loads (120a) and (120b) can be connected to the power bus over the two first power channels (1090) and (1095) or one of the two power loads (120a) and (120b) can be connected to the power bus over the output power converter via the second power channel (1095) while the other of the two power loads (120a) and (120b) is connected to the power bus over the relative first channel (1090) or (1095). While not shown in FIG. 2 the remaining pair of output device ports (totaling six ports) is configured like the output device ports (110a) and (110b). Thus all six device ports of the device (100) include a first power channel for directly connecting an external device connected to the device port to the power bus when the first controllable switch disposed along the first power channel is closed. Meanwhile at the two input device ports (130a) and (130b) share an input power converter and each pair of output device ports shares an output power converter.
2.2.1 Empty Input Device Ports not Utilized
Accordingly one problem with the device disclosed by Robinson et al. is that for a given pair of device ports only one of the device ports has access to a power converter. In the case of the input device ports (130a, 130b) the input power converter (1065) can operate with one power conversion setting, e.g. to step up or step down the input voltage to match the bus voltage. Thus if two input sources are available and each has a different non-bus compatible operating voltage, only one of the two input sources is usable and one of the input device ports is available. While the unused input port can be used as an output port for a power load that is bus voltage compatible there is no opportunity to use the empty input port for a non-bus compatible voltage device. The problem also extends to the output side. As a result one of the input ports is not usable. In the case of the output device ports (110a, 110b) and other pairs on the power manager, the output power converters (1065) can operate with one power conversion setting, e.g. to step up or step down the bus voltage to match the connected non-bus voltage compatible power load. Thus if two power loads are in need of power and each has a different non-bus compatible operating voltage, only one of the two power loads can be powered and one of the two output device ports associated with the output power converter is available. While the unused output port can be used as an output port for a power load that is bus voltage compatible there is no opportunity to use the empty output port for a non-bus compatible voltage device.
Thus one problem that arises with conventional power managers that do not include a power converter for each device ports is that not all the available device ports can be utilized to power loads that require a power conversion. In one example, the bus is powered by a single power source connected to one of the input device ports (130a, 130b) and there are more than four power loads that need power. In this example four power loads may be able to be powered at the four output ports (110) but one of the input ports (130) is empty. While the empty input port can be utilized to power a load with a bus compatible operating voltage there is a need to utilize the empty input port to power a load that needs a power conversion. More generally there is a need to utilize empty input and output device ports to power loads that require a power conversion.
2.2.2 Power Loss Resulting from Each Power Conversion
A further problem in the art relates to suffering power losses associated with each power conversion. As is well known, each power conversion (e.g. a buck/boost converter) has an associated power loss in proportion to the input and output voltage and the input and output current amplitude. The power loss for such a conversion for a defined set of input and output currents can be approximated by:PLoss=Ls(|Vin−Vout|)  Equation 1where the power loss PLoss is the power lost due to the voltage conversion for given input and output current amplitudes, Ls is a loss factor associated with the particular power converter or type of power converter, Vin is the input voltage, and Vout is the output voltage. Thus the power loss is directly proportional to the step up or step down voltage.2.2.3 Fixed Bus Voltage can Lead to Power Loss
When a power manager (e.g. 200) is operated with a fixed bus voltage, unnecessarily large step up and step down voltage conversions are sometimes performed, leading to unnecessary power loss. Moreover, as described above, operating a power manager with a fixed bus voltage can lead to empty device ports that are not usable to power loads. Since all the device ports of the device shown in FIG. 2 include a power channel to directly connect a power device to the power bus without a power conversion, allowing the bus voltage to match the voltage of at least some of the power devices connected to the power bus can help to avoid power conversions. Alternately reducing the step up or step down voltage at each converter can also reduce power conversion losses.
In a conventional operating mode, a fixed bus voltage ranges from 12-16 volts, but the user has a 30 volt power supply and a plurality of 30 volt power loads that need to be connected to the power manager. In this case, each 30 volt device requires a power conversion to connect to the power bus. When each device is power converted, power losses occur at each device port. Given that in many cases, power managers are used in remote locations to simultaneously power a plurality of power loads using limited input power resources, a power loss at every device port is not desirable. Thus, there is a need in the art for a power manager that can adapt its bus voltage according to the configuration of power devices connected to it to reduce power loss and maximize device port utilization.